An automatic core setting machine is disclosed in Hunter U.S. patent application, Ser. No. 680,478, filed Dec. 11, 1984, now U.S. Pat. No. 4,590,982. In that machine, the cores are carried in pockets in a mask from a tilted receiving position to a horizontal position with the cores facing downward. During movement of the mask, the cores are held in the mask by applying suction to the core pockets by means of a vacuum pump. Due to sand particles loosened from the sand molds and drawn into the vacuum system, however, previously used vacuum pumps have experienced clogging, premature wear and failure.